That's not because it will alter the energy landscape in the short term. The US government expects that nuclear power will continue to provide about 20 per cent of the US electricity supply between now and 2035. The new plants will simply replace the output of ageing reactors being shut down by utility companies.

Nonetheless, it's a step in the right direction. As we recently argued (9 March, page 3), nuclear energy is uniquely useful in reducing our impact on the climate. For all its drawbacks, it is currently the only low-carbon technology that can supply stable power on a very large scale.

But the renaissance has not dawned yet. Some older nuclear plants simply can't compete on cost with gas-fuelled rivals. Newer designs should help close the gap, but fossil fuels' cost-effectiveness is driven, in part, by a licence to emit carbon dioxide. So for nuclear to gain ground, President Barack Obama will have to back up his tough talk about legislation mandating carbon cuts with economic incentives. He's already offered a carrot, in the form of an $8.3 billion commitment to finance the nuclear plants' construction; imposing financial penalties on carbon-intensive power would provide a stick.

This is unlikely to happen overnight. But even if it did, any nuclear renaissance is still likely be a long process. Today's plants take a lot of money, time and expertise to build, limiting their deployment and diminishing their commercial appeal.

That might change in the future. The US Department of Energy is co-sponsoring a project to see whether small modular reactors (SMRs), each producing about 180 megawatts (compared with 1000 megawatts from a full-sized reactor) can be made cost-effective.

If they can, SMRs could be built in factories and shipped wherever they are needed. There are obvious security concerns, but if this idea works, it really might kick off a nuclear renaissance – and one that would span the globe.

This article appeared in print under the headline "At the crack of dawn"

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